U.S. patent number 6,958,064 [Application Number 10/713,357] was granted by the patent office on 2005-10-25 for systems and methods for performing simultaneous ablation.
This patent grant is currently assigned to Boston Scientific SciMed, Inc.. Invention is credited to Robert Garabedian, Jerry Jarrard, Robert F. Rioux.
United States Patent |
6,958,064 |
Rioux , et al. |
October 25, 2005 |
Systems and methods for performing simultaneous ablation
Abstract
A system for treating tissue includes first and second ablation
devices each including a plurality of wire electrodes and coupled
to a generator in parallel. In one embodiment, the generator
includes first and second terminals coupled in parallel to one
another, and the first and second ablation devices are connected to
the first and second terminals, respectively. Alternatively, the
first and second ablation devices are coupled to a single terminal
of the generator using a "Y" cable. A ground electrode is coupled
to the generator opposite the first and second ablation devices for
monopolar operation. The first and second arrays of electrodes are
inserted into first and second sites adjacent one another within a
tissue region. Energy is simultaneously delivered to the first and
second arrays to generate lesions at the first and second sites
preferably such that the first and second lesions overlap.
Inventors: |
Rioux; Robert F. (Ashland,
MA), Garabedian; Robert (Tyngsboro, MA), Jarrard;
Jerry (Sunnyvale, CA) |
Assignee: |
Boston Scientific SciMed, Inc.
(Maple Grove, MN)
|
Family
ID: |
34573694 |
Appl.
No.: |
10/713,357 |
Filed: |
November 14, 2003 |
Current U.S.
Class: |
606/41; 606/42;
607/102 |
Current CPC
Class: |
A61B
18/148 (20130101); A61B 18/1206 (20130101); A61B
2018/00702 (20130101); A61B 2018/00875 (20130101); A61B
2018/143 (20130101); A61B 2018/1475 (20130101) |
Current International
Class: |
A61B
18/14 (20060101); A61B 018/18 () |
Field of
Search: |
;606/41,42,45-50
;607/100-102 ;604/21,22,1 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
WO99/04710 |
|
Feb 1999 |
|
WO |
|
WO00/06046 |
|
Feb 2000 |
|
WO |
|
Other References
PCT International Search Report for PCT/US2004/036479, Applicant:
Scimed Life Systems, Inc., Forms PCT/ISA/210 and 220, dated Feb. 8,
2005 (7 pages). .
PCT Written Opinion of the International Search Authority for
PCT/US2004/036479, Applicant: Scimed Life Systems, Inc., Form
PCT/ISA/237, dated Feb. 8, 2005 (4 pages)..
|
Primary Examiner: Rollins; Rosiland
Attorney, Agent or Firm: Bingham McCutchen LLP
Claims
What is claimed:
1. A system for treating tissue within a tissue region using
electrical energy, comprising: a source of electrical energy; a
first ablation device comprising a first structure and a plurality
of electrodes coupled to the source of energy; and a second
ablation device comprising a second structure and a plurality of
electrodes coupled to the source of energy in parallel with the
first ablation device, whereby the first and second ablation
devices can substantially simultaneously create first and second
lesions, respectively, within a tissue region, wherein the first
structure and the second structure are independently moveable
relative to each other; and a ground electrode coupled to the
source of energy opposite the first and second ablation
devices.
2. The system of claim 1, wherein the source of electrical energy
comprises first and second terminals coupled in parallel to one
another, and wherein the first ablation device is coupled to the
first terminal and the second ablation device is coupled to the
second terminal.
3. The system of claim 2, wherein the source of electrical energy
comprises first and second control circuits coupled to the first
and second terminals, respectively, in parallel with one another,
the first and second control circuits providing impedance feedback
for the first and second terminals, respectively.
4. The system of claim 1, wherein the source of electrical energy
comprises a terminal, and wherein the system further comprises a
"Y" cable coupled between the first and second ablation devices and
the terminal.
5. The system of claim 1, wherein the source of electrical energy
is a radio frequency (RF) generator.
6. The system of claim 1, wherein the source of electrical energy
comprises circuitry for determining impedance between the first and
second ablation devices and the ground electrode.
7. The system of claim 1, wherein at one of the first and second
ablation devices comprises an array of wires deployable from a
cannula, the array of wires comprising the plurality of
electrodes.
8. The system of claim 1, wherein the first ablation device and the
second ablation device are independently moveable relative to each
other.
9. A method for creating a lesion within a tissue region, the
method comprising: inserting a first array of electrodes carried by
a first structure into a first site within a tissue region;
inserting a second array of electrodes carried by a second
structure into a second site within the tissue region, the second
array of electrodes being coupled in parallel with the first array
of electrodes, wherein the first structure and the second structure
are independently moveable relative to each other; and
simultaneously delivering energy to the first and second arrays of
electrodes to generate lesions at the first and second sites within
the tissue region.
10. The method of claim 9, further comprising coupling the first
and second arrays of electrodes to a source of electrical
energy.
11. The method of claim 10, wherein the first and second arrays of
electrodes are coupled to the source of electrical energy by
connecting the first ablation device to a first output terminal of
the source of electrical energy and connecting the second ablation
device to a second output terminal of the source of electrical
energy.
12. The method of claim 10, wherein the first and second arrays of
electrodes are coupled to the source of electrical energy by
coupling one end of a connector to a terminal of the source of
electrical energy, and coupling parallel ends of the connector to
the first and second arrays of electrodes.
13. The method of claim 12, wherein the connector comprises a "Y"
cable.
14. The method of claim 9, further comprising removing at least one
of the first and second arrays of electrodes from the tissue region
and introducing the at least one of the first and second arrays of
electrode into a third site within the tissue region.
15. The method of claim 9, wherein the first and second arrays of
electrodes are introduced into the first and second sites from
first and second cannulas, respectively.
16. The method of claim 15, further comprising introducing the
first and second cannulas into the tissue region until distal ends
of the first and second cannulas are disposed adjacent the first
and second sites, respectively, and wherein the first and second
arrays of electrodes are deployed from the distal ends of the first
and second cannulas into the first and second sites,
respectively.
17. The method of claim 9, wherein the tissue region comprises a
liver.
18. The method of claim 9, wherein the tissue region comprises a
tumor.
19. The method of claim 18, wherein the first and second sites are
disposed adjacent to one another within the tumor such that the
first and second lesions at least partially overlap.
20. The method of claim 9, wherein the first array of electrodes
and the second array of electrodes are independently moveable
relative to each other.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The field of the invention relates to medical devices, and more
particularly, to systems and methods for ablating or otherwise
treating tissue using electrical energy.
2. Background of the Invention
Tissue may be destroyed, ablated, or otherwise treated using
thermal energy during various therapeutic procedures. Many forms of
thermal energy may be imparted to tissue, such as radio frequency
electrical energy, microwave electromagnetic energy, laser energy,
acoustic energy, or thermal conduction.
In particular, radio frequency ablation (RFA) may be used to treat
patients with tissue anomalies, such as liver anomalies and many
primary cancers, such as cancers of the stomach, bowel, pancreas,
kidney and lung. RFA treatment involves the destroying undesirable
cells by generating heat through agitation caused by the
application of alternating electrical current (radio frequency
energy) through the tissue.
Various RF ablation devices have been suggested for this purpose.
For example, U.S. Pat. No. 5,855,576 describes an ablation
apparatus that includes a plurality of wire electrodes deployable
from a cannula or catheter. Each of the wires includes a proximal
end that is coupled to a generator, and a distal end that may
project from a distal end of the cannula. The wires are arranged in
an array with the distal ends located generally radially and
uniformly spaced apart from the catheter distal end. The wires may
be energized in a monopolar or bipolar configuration to heat and
necrose tissue within a precisely defined volumetric region of
target tissue. The current may flow between closely spaced wire
electrodes (bipolar mode) or between one or more wire electrodes
and a larger; common electrode (monopolar mode) located remotely
from the tissue to be heated. To assure that the target tissue is
adequately treated and/or to limit damaging adjacent healthy
tissues, the array of wires may be arranged uniformly, e.g.,
substantially evenly and symmetrically spaced-apart so that heat is
generated uniformly within the desired target tissue volume. Such
devices may be used either in open surgical settings, in
laparoscopic procedures, and/or in percutaneous interventions.
During tissue ablation, the maximum heating often occurs in the
tissue immediately adjacent the emitting electrodes. In general,
the level of tissue heating is proportional to the square of the
electrical current density, and the electrical current density in
tissue generally falls rapidly with increasing distance from the
electrode. The decrease of a current density depends upon a
geometry of the electrode. For example, if the electrode has a
spherical shape, the current density will generally fall as the
second power of distance from the electrode. On the other hand, if
the electrode has an elongate shape (e.g., a wire), the current
density will generally fall with distance from the electrode, and
the associated power will fall as the second power of distance from
the electrode. For the case of spherical electrode, the heating in
tissue generally falls as the fourth power of distance from the
electrode, and the resulting tissue temperature therefore decreases
rapidly as the distance from the electrode increases. This causes a
lesion to form first around the electrodes, and then to expand into
tissue disposed further away from the electrodes.
Due to physical changes within the tissue during the ablation
process, the size of the lesion created may be limited. For
example, the concentration of heat adjacent to wires often causes
the local tissue to desiccate, thereby reducing its electrical
conductivity. As the tissue conductivity decreases, the impedance
to current passing from the electrode to the tissue increases so
that more voltage must be supplied to the electrodes to affect the
surrounding, more distant tissue. The tissue temperature proximate
to the electrode may approach 100.degree. C., so that water within
the tissue boils to become water vapor. As this desiccation and/or
vaporization process continues, the impedance of the local tissue
may rise to the point where a therapeutic level of current can no
longer pass through the local tissue into the surrounding
tissue.
Thus, the rapid fall-off in current density may limit the volume of
tissue that can be treated by the wire electrodes. As such,
depending upon the rate of heating and the size of the wire
electrodes, existing ablation devices may not be able to create
lesions that are relatively large in size. Longer wire electrodes
and/or larger arrays have been suggested for creating larger
lesions. The effectiveness of such devices, however, may be limited
by the desiccation and/or vaporization process discussed
previously. While wire electrodes can be deployed, activated,
retracted, and repositioned sequentially to treat multiple
locations within a tissue region, such an approach may increase the
length of time of a procedure, and precise positioning to ensure
that an entire tissue region is treated may be difficult to
accomplish.
Accordingly, improved systems and methods for tissue ablation would
be useful.
SUMMARY OF THE INVENTION
The present invention is directed to systems and methods for
delivering energy to tissue, and more particularly to systems and
methods for delivering energy substantially simultaneously to
multiple electrode arrays to increase a volume of tissue being
treated.
In accordance with a first aspect of the present invention, a
system for treating tissue within a tissue region is provided that
includes a source of energy, a first ablation device including a
plurality of wires coupled to the source of energy, and a second
ablation device including a plurality of wires coupled to the
source of energy in parallel with the first ablation device,
whereby the first and second ablation devices can substantially
simultaneously create first and second lesions, respectively,
within a tissue region.
In a preferred embodiment, the wires of the first and second
ablation devices are electrodes and the source of energy is a
source of electrical energy, e.g., a radio frequency (RF)
generator. Preferably, the first and second ablation devices
include an array of wires deployable from a cannula.
The source of electrical energy may include first and second
terminals coupled in parallel to one another. The first ablation
device may be coupled to the first terminal and the second ablation
device may be coupled to the second terminal. Alternatively, the
source of electrical energy may include a terminal, and a "Y" cable
or other connector may be coupled between the first and second
ablation devices and the terminal to couple the first and second
ablation devices in parallel. Optionally, a ground electrode may be
coupled to the source of energy opposite the first and second
ablation devices, e.g., to provide a return path for electrical
energy delivered to the tissue from the electrodes.
In accordance with another aspect of the present invention, a
method is provided for creating a lesion within a tissue region,
e.g., a benign or cancerous tumor within a liver or other tissue
structure. A first array of electrodes may be inserted into a first
site within the tissue region, and a second array of electrodes may
be inserted into a second site within the tissue region.
Preferably, the second array of electrodes is coupled in parallel
with the first array of electrodes, e.g., to a RF generator or
other source of energy.
In one embodiment, the first and second arrays of electrodes may be
introduced into the first and second sites from first and second
cannulas, respectively. Preferably, the first and second cannulas
are introduced into the tissue region until distal ends of the
first and second cannulas are disposed adjacent the first and
second sites, respectively. The first and second arrays of
electrodes may then be deployed from the distal ends of the first
and second cannulas into the first and second sites,
respectively.
Energy may be substantially simultaneously delivered to the first
and second arrays of electrodes to generate lesions at the first
and second sites within the tissue region. Preferably, the first
and second sites are disposed adjacent to one another within the
tissue region such that the first and second lesions at least
partially overlap. Optionally, at least one or both of the first
and second arrays of electrodes may be removed from the tissue
region and introduced into a third (and fourth) site within the
tissue region, and activated to increase the size of the lesion
created. In other embodiments, the first and second arrays of
electrodes can be placed at different sites, each of which is
associated with a treatment region. In such arrangement, separate
tissues at different treatment sites can be ablated
simultaneously.
Other aspects and features of the invention will be evident from
reading the following detailed description of the preferred
embodiments, which are intended to illustrate, not limit, the
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
The drawings illustrate the design and utility of preferred
embodiments of the present invention, in which similar elements are
referred to by common reference numerals. In order to better
appreciate how advantages and objects of the present inventions are
obtained, a more particular description of the present inventions
briefly described above will be rendered by reference to specific
embodiments thereof, which are illustrated in the accompanying
drawings. Understanding that these drawings depict only typical
embodiments of the invention and are not therefore to be considered
limiting its scope, the invention will be described and explained
with additional specificity and detail through the use of the
accompanying drawings.
FIG. 1 illustrates a system for delivering electrical energy to
tissue, in accordance with a preferred embodiment of the present
invention.
FIG. 2 illustrates a variation of the ablation system of FIG. 1,
showing the power supply having a plurality of output
terminals.
FIG. 3 is a cross-sectional side view of an embodiment of an
ablation device, showing electrode wires constrained within a
cannula.
FIG. 4 is a cross-sectional side view of the ablation device of
FIG. 3, showing the wires deployed from the cannula.
FIGS. 5A-5D are cross-sectional views, showing a method for
treating tissue, in accordance with the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the drawings, in which similar or corresponding
parts are identified with the same reference numeral, FIG. 1 shows
a preferred embodiment of an ablation system 10, in accordance with
the present invention. The ablation system 10 includes a source of
energy 12, e.g., a radio frequency (RF) generator, having an output
terminal 14, a connector 16, a first ablation device 18, and a
second ablation device 20. One or both of the first and the second
ablation devices 18, 20 may be capable of being coupled to the
generator 12.
The generator 12 is preferably capable of operating with a fixed or
controlled voltage so that power and current diminish as impedance
of the tissue being ablated increases. Exemplary generators are
described in U.S. Pat. No. 6,080,149, the disclosure of which is
expressly incorporated by reference herein. The preferred generator
12 may operate at relatively low fixed voltages, typically below
one hundred fifty volts (150 V) peak-to-peak, and preferably
between about fifty and one hundred volts (50-100 V). Such radio
frequency generators are available from Boston Scientific
Corporation, assignee of the present application, as well as from
other commercial suppliers. It should be noted that the generator
12 is not limited to those that operate at the range of voltages
discussed previously, and that generators capable of operating at
other ranges of voltages may also be used.
The connector 16 includes an input terminal 22, a first output
terminal 24, and a second output terminal 26 that is connected in
parallel with the first output terminal 24. The first and second
output terminals 24 and 26 of the connector 16 are configured for
coupling to the first and second ablation devices 18, 20,
respectively, while the input terminal 22 of the connector 16 is
configured for coupling to the output terminal 14 of the generator
12. Optionally, the ablation system 10 may include one or more
cables 28, e.g., extension cables or cables that extend from the
first and second ablation devices 18, 20. If cables 28 are not
provided, the first and second ablation devices 18, 20 may be
coupled directly to the output terminals 24 and 26, respectively,
of the connector 16. In the illustrated embodiment, the connector
16 may deliver power from the generator 12 simultaneously to the
first and second ablation devices 18, 20. If it is desired to
deliver power to more than two ablation devices, the connector 16
may have more than two output terminals connected in parallel to
one another (not shown).
Alternatively, as shown in FIG. 2, instead of the "Y" connector 16,
a generator 12' may be provided that includes two (or optionally
more) output terminals 14' coupled in parallel with one another. In
this case, first and second ablation devices 18,' 20' may be
coupled to separate output terminals 14' of the generator 12'
without requiring a connector 16 (not shown, see FIG. 1). However,
if the generator 12' does not provide an adequate number of output
terminals 14 for the number of ablation devices desired, one or
more connectors 16 (not shown) may be used to couple two or more
ablation devices to a single output terminal of the generator
12.'
The output terminals 14' of the generator 12' may be coupled to
common control circuits (not shown) within the generator 12.'
Alternatively, the generator 12' may include separate control
circuits coupled to each of the output terminals 14.' The control
circuits may be connected in parallel with one another, yet may
include separate impedance feedback to control energy delivery to
the respective output terminals 14.' Thus, the output terminals 14'
may be connected in parallel to an active terminal of the generator
12' such that the ablation devices 18,' 20' deliver energy to a
common ground pad electrode (not shown) in a monopolar mode.
Alternatively, the output terminals 14' may be connected to
opposite terminals of the generator 12' for delivering energy
between the ablation devices 18,' 20' in a bipolar mode.
Turning to FIGS. 3 and 4, in a preferred embodiment, each of the
ablation devices 18, 20 of FIG. 1 (or alternatively, the ablation
devices 18,' 20' of FIG. 2) may be a probe assembly 50. The probe
assembly 50 may include a cannula 52 having a lumen 54, a shaft 56
having a proximal end 58 and a distal end 60, and a plurality of
electrode wires 62 secured to the distal end 60 of the shaft 56.
The proximal end 58 of the shaft 56 may include a connector 63 for
coupling to the generator 12. For example, the connector 62 may be
used to connect the probe assembly 50 to a cable 66, which may be
part of the connector 16 (not shown, see FIG. 1), an extension
cable, or a cable that extends from the output terminal 14 of the
generator 12. Alternatively, the probe assembly 50 may itself
include a cable (not shown) on the proximal end 58 of the shaft 56,
and a connector may be provided on the proximal end of the cable
(not shown).
The cannula 52 may have a length between about five and thirty
centimeters (5-30 cm), and/or an outer diameter or cross sectional
dimension between about one and five millimeters (1-5 mm). However,
the cannula 52 may also have other lengths and outer cross
sectional dimensions, depending upon the application. The cannula
52 may be formed from metal, plastic, and the like, and/or may be
electrically active or inactive within the probe assembly 50,
depending upon the manner in which electrical energy is to be
applied.
The cannula 52 may coaxially surround the shaft 56 such that the
shaft 56 may be advanced axially from or retracted axially into the
lumen 54 of the cannula 52. Optionally, a handle 64 may be provided
on the proximal end 58 of the shaft 56 to facilitate manipulating
the shaft 56. The wires 62 may be compressed into a low profile
when disposed within the lumen 54 of the cannula 52, as shown in
FIG. 3. As shown in FIG. 4, the proximal end 58 of the shaft 56 or
the handle 64 (if one is provided) may be advanced to deploy the
wires from the lumen 54 of the cannula 52. When the wires 62 are
unconfined outside the lumen 54 of the cannula 52, they may assume
a relaxed expanded configuration. FIG. 4 shows an exemplary
two-wire array including wires 62 biased towards a generally "U"
shape and substantially uniformly separated from one another about
a longitudinal axis of the shaft 56. Alternatively, each wire 62
may have other shapes, such as a "J" shape, and/or the array may
have one wire 62 or more than two wires 62. The array may also have
non-uniform spacing to produce an asymmetrical lesion. The wires 62
are preferably formed from spring wire, superelastic material, or
other material, such as Nitinol, that may retain a shape memory.
During use of the probe assembly 50, the wires 62 may be deployed
into a target tissue region to deliver energy to the tissue to
create a lesion.
Optionally, a marker (not shown) may be placed on the handle 64
and/or on the proximal end 58 of the shaft 56 for indicating a
rotational orientation of the shaft 56 during use. The probe
assembly 50 may also carry one or more radio-opaque markers (not
shown) to assist positioning the probe assembly 50 during a
procedure, as is known in the art. Optionally, the probe assembly
50 may also include a sensor, e.g., a temperature sensor and/or an
impedance sensor (not shown), carried by the distal end of the
shaft 56 and/or one or more of the wires 62.
Exemplary ablation devices having a spreading array of wires have
been described in U.S. Pat. No. 5,855,576, the disclosure of which
is expressly incorporated by reference herein.
It should be noted that the ablation devices 18, 20 are not
necessarily limited to the probe assembly 50 shown in FIGS. 3 and
4, and that either or both of the ablation devices 18, 20 may be
selected from a variety of devices that are capable of delivering
ablation energy. For example, medical devices may also be used that
are configured for delivering ultrasound energy, microwave energy,
and/or other forms of energy for the purpose of ablation, which are
well known in the art. Furthermore, the first and second ablation
devices 18, 20 are not necessarily limited to the same type of
devices. For example, the first ablation device 18 may deliver
ultrasound energy while the second ablation device 20 may deliver
radio-frequency energy. Also, the first and second ablation devices
18, 20 may have different sizes of arrays of wires 62, and/or
different types or numbers of electrodes. For example, either of
the first and second ablation devices 18, 20 may be an elongate
member carrying a single electrode tip.
Referring now to FIGS. 5A-5D, the ablation system 10 may be used to
treat a treatment region TR within tissue located beneath skin or
an organ surface S of a patient. The tissue TR before treatment is
shown in FIG. 5A. As shown in FIG. 5B, the cannulas 52 of the first
and second ablation devices 18, 20 may be introduced into the
treatment region TR, so that the respective distal ends of the
cannulas 52 of the first and second ablation devices 18, 20 are
located at first and second target sites TS1, TS2. This may be
accomplished using any of a variety of techniques. In some cases,
the cannulas 52 and shafts 56 of the respective ablation devices
18, 20 may be introduced into the target site TS percutaneously,
i.e., directly through the patient's skin, or through an open
surgical incision. In this case, the cannulas 52 may have a
sharpened tip, e.g., a beveled or pointed tip, to facilitate
introduction into the treatment region. In such cases, it is
desirable that the cannulas 52 be sufficiently rigid, i.e., have
sufficient column strength, so that the cannulas 52 may be
accurately advanced through tissue.
In an alternative embodiment, the cannulas 52 may be introduced
without the shafts 56 using internal stylets (not shown). Once the
cannulas 52 are positioned as desired, the stylets may be exchanged
for the shafts 56 that carry the wires 62. In this case, each of
the cannulas 52 may be substantially flexible or semi-rigid, since
the initial column strength of the apparatus 10 may be provided by
the stylets. Various methods known in the art may be utilized to
position the probe 50 before deploying the wires.
In a further alternative, one or more components or elements may be
provided for introducing each of the cannulas 52 to the treatment
region. For example, a conventional sheath and sharpened obturator
(stylet) assembly (not shown) may be used to access the target
site(s). The assembly may be positioned using ultrasonic or other
conventional imaging. Once properly positioned, the
obturator/stylet may be removed, providing an access lumen through
the sheath. The cannula 52 and shaft 56 of each of the ablation
devices 18, 20 may then be introduced through the respective sheath
lumens so that the distal ends of the cannulas 52 of the first and
second ablation devices 18, 20 advance from the sheaths into the
target sites TS1, TS2.
Turning to FIG. 5C, after the cannulas 52 of the ablation devices
18, 20 are properly placed, the shafts 56 of the respective
ablation devices 18, 20 may be advanced distally, thereby deploying
the arrays of wires 62 from the distal ends of the respective
cannulas 52 into the target sites TS1, TS2. Preferably, the wires
62 are biased to curve radially outwardly as they are deployed from
the cannulas 52. The shaft 56 of each of the ablation devices 18,
20 may be advanced sufficiently such that the wires 62 fully deploy
to circumscribe substantially tissue within the target sites TS1,
TS2 of the treatment region TR, as shown in FIG. 5D. Alternatively,
the wires 62 may be only partially deployed or deployed
incrementally in stages during a procedure.
If the generator 12 of the ablation system 10 includes only one
output terminal 14, one or more connectors 16, described
previously, may be used to couple the ablation devices 18, 20 to
the output terminal 14. If the generator 12 includes more than one
output terminals 14, the ablation devices 18, 20 may be coupled
directly to the generator 12 without using the connector 16.
Extension cables 28 may also be used to couple the ablation devices
18, 20 to the connector 16 or to the generator 12. The ablation
devices 18, 20 may be coupled to the generator 12 in parallel with
one another after the wires 62 of the respective ablation devices
18, 20 have been deployed. Alternatively, the wires 62 may be
coupled to the generator 12 before the cannulas 52 are introduced
to the treatment region, or at any time before the tissue is
ablated. A neutral or ground electrode, e.g., an external electrode
pad, may be coupled to the opposite terminal (not shown) of the
generator 12 and coupled to the patient, e.g., the patient's skin,
in a conventional manner.
Next, energy, preferably RF electrical energy, may be delivered
from the generator 12 to the wires 62 of the respective ablation
devices 18, 20, thereby substantially simultaneously creating
lesions at the first and second target sites TS1, TS2 of the
treatment region TR, respectively. Because the ablation devices 18,
20 are connected in parallel to the generator 12, as the impedance
of tissue at one of the target sites TS1, TS2 increases, e.g., as
the tissue is desiccated or otherwise treated, current may continue
to flow to the other target site(s) to complete treatment of both
target sites.
Simultaneously creating two or more lesions within a treatment
region may substantially reduce the duration of an ablation
procedure. In addition, using only a single generator 12 (or fewer
generators than deployed ablation devices) may reduce the cost of
equipment necessary to complete a procedure. When desired lesions
at the first and second target sites TS1, TS2 of the treatment
region TR have been created, the wires 62 of each of the ablation
devices 18, 20 may be retracted into the respective lumens 54 of
the cannulas 52, and the ablation devices 18, 20 may be removed
from the treatment region TR. In many cases, two ablation devices
18, 20 may be sufficient to create a desired lesion. However, if it
is desired to perform further ablation to increase the lesion size
or to create lesions at different site(s) within the treatment
region TR or elsewhere, the wires 62 of either or both of the
ablation devices 18, 20 may be introduced and deployed at different
target site(s), and the same steps discussed previously may be
repeated.
Although an embodiment has been described with reference to placing
ablation devices at different sites that are within a treatment
region, the scope of the invention should not be so limited. In
alternative embodiments, the ablation devices 18, 20 are disposed
at different sites, each of which is associated with a treatment
region. In such arrangement, separate tissues at different sites
can be ablated simultaneously. In addition, it should be noted that
the scope of the invention should not be limited to the ablation
system 10 having two ablation devices. In alternative embodiments,
the ablation system 10 can have more than two ablation devices.
Thus, although several preferred embodiments have been shown and
described, it would be apparent to those skilled in the art that
many changes and modifications may be made thereunto without the
departing from the scope of the invention, which is defined by the
following claims and their equivalents.
* * * * *